Congenital Heart Diseases for NEET PG — Complete Guide 2026

Version 1.0 — Published March 2026

Congenital heart disease (CHD) is a structural abnormality of the heart or great vessels present at birth — occurring in 8–10 per 1,000 live births and representing the most common category of birth defects. In NEET PG, CHD questions span pediatrics (clinical presentation, management), medicine (adult survivors with Eisenmenger), surgery (operative approaches), and radiology (CXR patterns). The student who can classify every lesion by hemodynamics (shunt direction, cyanosis, pulmonary blood flow) and recognize the classic imaging patterns will capture marks across multiple subjects.

This guide covers the complete spectrum of CHDs with the hemodynamic explanations, clinical clues, and imaging findings that NBE tests. Pair this with practice on the Pediatrics subject hub and cross-reference high-yield pediatrics topics for additional neonatal and childhood cardiology content.

Classification — acyanotic vs cyanotic

Congenital heart disease classification divides lesions into acyanotic (no cyanosis at presentation) and cyanotic (cyanosis present) based on the direction and nature of intracardiac shunting — this is the foundational framework for every CHD question.

Key hemodynamic principle: Left-to-right shunts initially cause volume overload of the pulmonary circulation (pulmonary plethora on CXR, heart failure in infants). Over years, the chronic volume overload causes pulmonary vascular remodeling → fixed pulmonary hypertension → Eisenmenger syndrome (shunt reversal).

VSD — the most common CHD

Ventricular septal defect (VSD) is an abnormal opening in the interventricular septum allowing left-to-right shunting of blood — accounting for 25–30% of all congenital heart defects and being the single most common CHD.

VSD types

Clinical features by VSD size

NBE trap: The loudest VSD murmur comes from the SMALLEST VSD (the pressure gradient across a small restrictive defect is high). A large VSD may have a soft murmur because the equalized pressures create minimal gradient. "Quiet VSD" = large VSD = urgently needs surgery.

Associated finding: Maladie de Roger — an isolated, small, perimembranous VSD with a loud pansystolic murmur but no hemodynamic significance.

ASD — the septal defect with fixed split S2

Atrial septal defect (ASD) is an abnormal opening in the interatrial septum — the second most common CHD, often asymptomatic until adulthood.

ASD types

Clinical features

• Fixed splitting of S2 — the hallmark physical finding. In ASD, the right ventricle has constant volume overload regardless of respiration, so A2-P2 splitting does not vary with breathing. (Normal splitting varies: widens on inspiration, narrows on expiration.)
• Ejection systolic murmur at upper left sternal border — relative pulmonary stenosis (increased flow across normal pulmonary valve)
• Mid-diastolic rumble at lower left sternal border — increased flow across tricuspid valve (only with significant shunts)
• CXR: Cardiomegaly, prominent pulmonary arteries, pulmonary plethora
• ECG: Incomplete RBBB + right axis deviation (secundum) or left axis deviation (primum)

Treatment: Device closure (catheter-based) for secundum ASD with adequate rims. Surgical closure for primum ASD, sinus venosus ASD, and large secundum ASDs without adequate rims.

PDA — the ductus that should have closed

Patent ductus arteriosus (PDA) is the persistence of the fetal connection between the aorta and pulmonary artery beyond 72 hours of birth — normally closing functionally within 10–15 hours of birth in response to increased oxygen tension and falling prostaglandin levels.

Anatomy: Connects the aortic isthmus (just distal to left subclavian artery) to the left pulmonary artery.

Clinical features:

• Continuous "machinery" murmur — best heard at the left infraclavicular area (below left clavicle). The murmur is continuous because the aortic pressure exceeds PA pressure throughout both systole and diastole.
• Bounding (water-hammer) pulses — wide pulse pressure from aortic diastolic runoff into the PA
• Differential cyanosis — lower limb cyanosis with pink upper limbs (when PDA + Eisenmenger syndrome develops)

Management:

• Premature neonates: Pharmacological closure with indomethacin or ibuprofen (prostaglandin synthesis inhibitors). Paracetamol (acetaminophen) is an emerging alternative.
• Term infants and children: Device closure (catheter-based, transcatheter coil or Amplatzer device) or surgical ligation
• When to keep PDA open: Duct-dependent lesions (TGA, pulmonary atresia, coarctation, HLHS) — use prostaglandin E1 (alprostadil) IV infusion to maintain ductal patency

NBE trap: Indomethacin closes the PDA (inhibits prostaglandins). Prostaglandin E1 opens/maintains the PDA. Know when each is needed.

Coarctation of the aorta

Coarctation of the aorta is a discrete narrowing of the aorta, typically at the level of the ligamentum arteriosum (just distal to the left subclavian artery) — presenting as upper limb hypertension with weak or absent femoral pulses.

Two presentations:

Classic clinical finding: Blood pressure gradient — upper limb BP >20 mmHg higher than lower limb BP. Radiofemoral delay (femoral pulse delayed compared to radial pulse).

Treatment: Balloon angioplasty with stenting (catheter-based) or surgical repair (resection with end-to-end anastomosis).

TOF — the most common cyanotic CHD

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease — comprising four anatomical abnormalities resulting from a single embryological defect: anterocephalad deviation of the outlet (infundibular) septum.

The four features:

1. Ventricular septal defect (large, unrestrictive)
2. Overriding aorta (aorta straddles the VSD)
3. Right ventricular outflow tract obstruction (infundibular pulmonary stenosis — determines severity)
4. Right ventricular hypertrophy (consequence of RVOTO)

Clinical features:

• Cyanosis (severity depends on degree of RVOTO)
• Tet spells (hypercyanotic spells) — sudden episodes of severe cyanosis with irritability, hyperpnea, and possible syncope. Triggered by crying, feeding, straining.
• Squatting — older children instinctively squat during tet spells (increases SVR → reduces right-to-left shunt → improves pulmonary blood flow)
• Clubbing — from chronic cyanosis

Investigations:

• CXR: Boot-shaped heart (coeur en sabot) — upturned apex from RVH + concave pulmonary artery segment (absent main PA shadow). Oligemic lung fields (reduced pulmonary blood flow).
• ECG: Right axis deviation, right ventricular hypertrophy

Tet spell management (stepwise)

1. Knee-chest position (infant) or squatting (child) — increases SVR
2. Oxygen — 100% by face mask
3. IV morphine — reduces respiratory drive and systemic oxygen consumption
4. IV phenylephrine — pure alpha-agonist, increases SVR directly
5. IV fluids — volume expansion
6. IV sodium bicarbonate — corrects metabolic acidosis
7. IV propranolol — for prevention of recurrent spells (relaxes infundibular muscle spasm)
8. Emergency BT shunt — if medical management fails (Blalock-Taussig shunt: subclavian → pulmonary artery)

Definitive surgery: Complete intracardiac repair — VSD closure + relief of RVOTO (infundibular resection + transannular patch). Optimal timing: 3–6 months of age.

TGA — the neonatal cyanotic emergency

Transposition of the great arteries (TGA) is the most common cyanotic CHD presenting in the neonatal period — characterized by the aorta arising from the right ventricle and the pulmonary artery from the left ventricle, creating two parallel circuits.

Hemodynamics: Systemic and pulmonary circulations run in parallel rather than in series. Without mixing (through ASD, VSD, or PDA), the condition is incompatible with life.

Clinical features:

• Severe cyanosis within hours of birth (progressive as PDA closes)
• Cyanosis NOT responding to oxygen (fixed right-to-left physiology)
• May be surprisingly well-appearing initially if mixing sites are adequate

Investigations:

• CXR: "Egg-on-a-string" (or egg-on-its-side) — narrow mediastinum (great vessels are parallel rather than crossing) + cardiomegaly with increased pulmonary vascularity
• ECG: Right axis deviation, RVH (normal for a neonate — not helpful for diagnosis)

Management:

1. Prostaglandin E1 — maintain PDA patency (immediate life-saving measure)
2. Rashkind balloon atrial septostomy — catheter-based creation of an ASD to allow mixing at atrial level (emergency palliative)
3. Arterial switch operation (Jatene procedure) — definitive surgery, ideally within first 2 weeks. The great arteries are transected and reconnected to the correct ventricles. Coronary arteries are reimplanted.

NBE point: The arterial switch must be performed within 2–3 weeks in simple TGA. After this, the left ventricle (pumping against low-pressure pulmonary circulation) loses muscle mass and cannot sustain systemic pressures after the switch.

Other cyanotic CHDs

Truncus arteriosus

Truncus arteriosus is a single arterial trunk arising from both ventricles, giving rise to the aorta, pulmonary arteries, and coronary arteries — always associated with a VSD.

• Associated with DiGeorge syndrome (22q11.2 deletion) — absent thymus, hypocalcemia, cardiac defects
• Cyanosis with increased pulmonary blood flow
• Treatment: Complete repair in the neonatal period (Rastelli procedure)

Total anomalous pulmonary venous return (TAPVR)

TAPVR is a condition where all four pulmonary veins drain into the systemic venous system instead of the left atrium — an ASD is mandatory for survival (the only pathway for oxygenated blood to reach the left side).

Types: Supracardiac (drains to SVC via vertical vein — most common), cardiac (drains to coronary sinus), infracardiac (drains below diaphragm to IVC/portal vein — worst prognosis due to obstruction), mixed.

CXR: "Snowman sign" (figure-of-8) — supracardiac type only. The dilated vertical vein, innominate vein, and SVC form the upper "snowball," and the heart forms the lower.

Treatment: Surgical — redirect pulmonary veins to left atrium + close ASD.

Eisenmenger syndrome

Eisenmenger syndrome is the irreversible reversal of a left-to-right shunt to right-to-left due to fixed pulmonary hypertension — the dreaded long-term complication of any large unrepaired left-to-right shunt (VSD, ASD, PDA, AVSD).

Pathophysiology:

1. Large left-to-right shunt → pulmonary overcirculation
2. Chronic volume/pressure overload → pulmonary vascular remodeling (intimal fibrosis, medial hypertrophy, plexiform lesions)
3. Pulmonary vascular resistance exceeds systemic vascular resistance
4. Shunt reverses: right-to-left → cyanosis, clubbing, polycythemia

Clinical features:

• Central cyanosis and clubbing (developing in a patient previously known to have an acyanotic lesion)
• Polycythemia (compensatory erythrocytosis → hyperviscosity → stroke risk)
• Hemoptysis (from bronchial collateral vessels)
• Syncope (reduced cardiac output)
• Right heart failure (eventually)

Key NBE point: Once Eisenmenger syndrome is established, surgical closure of the original defect is CONTRAINDICATED — removing the "pop-off" valve (the shunt) in the face of fixed pulmonary hypertension causes acute right heart failure and death.

Management:

• Pulmonary vasodilators: sildenafil (PDE5 inhibitor), bosentan (endothelin receptor antagonist)
• Phlebotomy only if symptomatic hyperviscosity (Hct >65%)
• Avoid: pregnancy (30–50% maternal mortality), dehydration, high altitude, general anesthesia
• Heart-lung transplant: only definitive option (rarely performed due to organ scarcity)

Diagnostic approach — CXR, ECG, and Echo findings

The diagnostic investigation findings per CHD lesion are tested directly — often as a "match the finding to the diagnosis" question.

CXR patterns

ECG patterns

Surgical management overview

Sources and references

1. Ghai Essential Pediatrics, 10th Edition (Paul et al., 2024) — Congenital heart disease classification, clinical features, and management protocols.
2. Nelson Textbook of Pediatrics, 22nd Edition (Kliegman et al., 2023) — Detailed embryology and hemodynamic descriptions of CHDs.
3. Park's Pediatric Cardiology for Practitioners, 7th Edition (Park, 2021) — ECG and CXR interpretation in congenital heart disease.
4. Harrison's Principles of Internal Medicine, 21st Edition (Loscalzo et al., 2022) — Adult congenital heart disease and Eisenmenger syndrome.
5. Sabiston Textbook of Surgery, 21st Edition (Townsend et al., 2022) — Surgical approaches for CHD correction.

Frequently asked questions

How many congenital heart disease questions appear in NEET PG?

Congenital heart disease contributes 3-5 questions per NEET PG paper across pediatrics, medicine, and surgery. The most tested topics are TOF (tet spell management), VSD (most common CHD), ASD (ostium secundum type), PDA (continuous machinery murmur), and Eisenmenger syndrome. CXR patterns like boot-shaped heart and egg-on-a-string are classic image-based questions.

What is the most common congenital heart disease?

Ventricular septal defect (VSD) is the most common congenital heart disease, accounting for 25-30% of all CHDs. The perimembranous (membranous) type is the most common VSD subtype. Small restrictive VSDs often close spontaneously by age 2 years. Large unrestrictive VSDs require surgical closure to prevent Eisenmenger syndrome.

What is the most common cyanotic congenital heart disease?

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease overall. TGA (transposition of great arteries) is the most common cyanotic CHD presenting in the neonatal period (first few days of life). The distinction between 'most common cyanotic CHD' (TOF) and 'most common cyanotic CHD in neonates' (TGA) is a classic exam trap.

How do I manage a tet spell in TOF?

Tet spell (hypercyanotic spell) management follows a stepwise approach: knee-chest position (increases SVR, reduces right-to-left shunting), oxygen supplementation, IV morphine (reduces respiratory drive and agitation), IV phenylephrine (increases SVR), IV fluids, IV sodium bicarbonate for acidosis. Propranolol is used for prevention of recurrent spells. Emergency surgery if medical management fails.

What is Eisenmenger syndrome?

Eisenmenger syndrome is the reversal of a left-to-right shunt to right-to-left due to pulmonary hypertension from chronic volume overload. Any large unrepaired left-to-right shunt (VSD, ASD, PDA) can cause Eisenmenger syndrome. Once established, surgical correction is contraindicated (the pulmonary vascular disease is irreversible). Treatment is medical: pulmonary vasodilators (sildenafil, bosentan). Heart-lung transplant is the only definitive option.

How do I differentiate ASD types in NEET PG?

Ostium secundum ASD (70% of ASDs) is at the fossa ovalis, causes fixed splitting of S2, and shows incomplete RBBB on ECG. Ostium primum ASD is an endocardial cushion defect associated with Down syndrome, causes left axis deviation on ECG, and often has a cleft mitral valve with MR. Sinus venosus ASD is near the SVC entry and is associated with anomalous right pulmonary vein drainage.

What CXR findings are tested for congenital heart diseases?

Boot-shaped heart (coeur en sabot) is TOF. Egg-on-a-string appearance is TGA. Snowman sign (figure-of-8) is TAPVR (supracardiac type). Box-shaped heart is Ebstein anomaly. Rib notching is coarctation of aorta (older children). Cardiomegaly with pulmonary plethora suggests large left-to-right shunt (VSD, PDA). Oligemic lung fields suggest reduced pulmonary blood flow (TOF, pulmonary atresia).

What is the role of prostaglandin E1 in congenital heart disease?

Prostaglandin E1 (alprostadil) maintains the patent ductus arteriosus open in duct-dependent lesions. It is life-saving in neonates with duct-dependent pulmonary circulation (TOF, pulmonary atresia, tricuspid atresia) where PDA provides pulmonary blood flow, and duct-dependent systemic circulation (coarctation, interrupted aortic arch, HLHS) where PDA provides systemic blood flow.

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Written by: NEETPGAI Editorial Team Reviewed by: Pending SME Review Last reviewed: March 2026

This article is reviewed by qualified medical professionals for clinical accuracy and exam relevance. For corrections or updates, contact the editorial team.